Sequential fracking procedures frequently involve the dropping of balls of progressively larger sizes for isolation of segments of a zone to be treated using a series of progressively larger ball seats. Typically devices that drop multiple balls associate a release plunger with each ball and vertically stack all the balls. These devices are top loaded and after inserting each ball the plunger above is extended to catch the next ball to be loaded. These devices tend to be heavy to set up, cumbersome to deal with a myriad of hydraulic control lines and expensive to fabricate and ship to the desired location. Typical of such designs are U.S. Pat. No. 8,256,514 and U.S. Publication 2013/0228326. In a variation of this theme the balls are stored in side chambers with a discrete actuator for each ball and the associated lines for hydraulically moving each ball into the central bore for dropping or pumping to the desired landing location. Some examples of such a design are U.S. Pat. Nos. 7,571,773 and 7,624,810. Some designs use applied pressure or pressure cycles to release discrete balls as shown in U.S. Pat. Nos. 7,100,700; 6,959,766 and 6,220,360. Yet other designs use a single plunger that releases a single ball with each stoke cycle where the balls are all the same size or the balls are of progressively larger sizes and the plunger opens a different amount in each cycle to release progressively bigger balls. Such designs are shown in U.S. Publication 2012/0152525 and 2012/0279717. In other designs the balls are stored in a recess outside the passage in the mandrel and rotation of the housing holding a ball aligns an outlet in the housing with a mandrel wall opening to release a ball as shown in U.S. Pat. No. 5,758,726. In another design involving relative rotation, the balls are in adjacent axial barrel chambers and barrel rotation successively aligns a barrel with a ball in it to an outlet path. This design places the balls in the same horizontal plane and has a very limited ball capacity as a result. This design is shown in U.S. Pat. No. 6,206,095. Other designs use a 90 degree mechanical rotation either by hand or with a power assist to rotate a support out from under a ball so that the ball can drop. These designs are shown in U.S. Pat. Nos. 6,715,541; 4,427,065; 5,590,713; 7,281,589; 6,776,228 and U.S. Publication 2013/0153237. The following references more generally relate to ball dropping devices but do not fall into any of the above described variations: U.S. Pat. No. 7,661,478 and U.S. Publication 2011/0174505.
What is needed and provided by the present invention is a ball dropping device that can hold enough different or same sized balls and is simple to build, load and operate. This is accomplished by a set of spaced parallel trays that have solid and open portions that are rotatable in tandem and operate in conjunction with stops that are stationary so that tray rotation causes balls to be stopped by the stationary stops as tray rotation brings an open portion of a tray under the ball and lets it fall through. This allows loading by periodic insertion of balls when the unit is empty that advance in tandem toward a lower end outlet with an adjacent flow line to allow pumping each dropped ball to its ultimate destination. A single driver such as a stepper motor makes the needed movements in the desired increments for all the trays. An indication of how many balls and their size that have been dropped can also be incorporated into the design. Those skilled in the art will better appreciate these and other aspects of the present invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.